


The New and Terrible River

by NanixErka



Category: Gravity Falls
Genre: Abandoned Work - Unfinished and Discontinued, Deer Dipper Pines, Deerper, Deertaur, Gargoyle Stan Pines, Gen, MerMabel, Mermaid Mabel Pines, Monster Falls AU, Mythical Beings & Creatures, One Shot, Wendy Courduroy (Mentioned), mud monster soos
Language: English
Status: Completed
Published: 2020-09-16
Updated: 2020-09-16
Packaged: 2021-03-07 17:00:26
Rating: General Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 4,103
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/26501035
Author URL: https://archiveofourown.org/users/NanixErka/pseuds/NanixErka
Summary: [...]He was off to investigate what was supposedly a magical river - identified in the book as “Fluvius Cantatis” Everything in the book was almost hilariously vague, most of the ciphers being far too complicated for him to begin to translate. The only thing writen about it in plain english was a warning at the top of the page.“DO NOT DRINK THE WATER”And that was concerning, since the river was apparently going to be the town’s new water source due to some dumb small town politics stuff. [...]
Relationships: Dipper Pines & Mabel Pines, Dipper Pines & Stan Pines, Jesus "Soos" Alzamirano Ramirez & Dipper Pines, Jesus "Soos" Alzamirano Ramirez & Mabel Pines, Jesus "Soos" Alzamirano Ramirez & Stan Pines, Mabel Pines & Stan Pines
Comments: 4
Kudos: 48





	The New and Terrible River

**Author's Note:**

> An unfinished story I rewrote. This was originally going to be a sprawling, long and dramatic fic, but unfortunately ADHD hit. 
> 
> I still think its fun, so enjoy! 
> 
> Please be advised that this is never going to be complete. Sorry

Dipper was fascinated with the amount of freedom he had while in Gravity Falls. His parents would have never just let him wander around in the town, with nothing more than money for food, or just… _explore_ the woods so long as he was back at a decent hour. With Grunkle Stan’s rather loose guardianship rules, he could do almost anything he wanted - from having chips for lunch to figuring out what was going on with the book. 

He was going solo on his adventure today - Mabel wanted to hang out with her friends and he “wasn’t invited”. He wasn’t offended. 

He was off to investigate what was supposedly a magical river - identified in the book as “Fluvius Cantatis” Everything in the book was almost hilariously vague, most of the ciphers being far too complicated for him to begin to translate. The only thing written about it in plain English was a warning at the top of the page. 

“DO NOT DRINK THE WATER” 

And that was concerning, since the river was apparently going to be the town’s new water source due to some dumb small town politics stuff. 

As he followed the map in the book, he remarked just how beautiful the day was. The weather in Gravity Falls was honestly pretty consistent and nice. The scattered clouds, the gentle breeze that kept the sun’s heat from getting too aggressive. A perfect day for all of the nonsense that he typically got up to. He pushed his hair out of his face, not caring much about anyone seeing his birthmark- and he climbed over a rather large log. 

And there it was, flowing calmly before him. 

Fluvius Cantatis was a rather wide river, with clear, flowing water. Looking into the river, he couldn’t see any fish, seaweed, or any organic life of any kind. Even the riverbank was bare of any grasses, it was nothing but mud. Further up the way, he could see that there were some rapids.

“Huh… weird” Dipper muttered, placing the book up on the log away from the river before getting himself closer to the water

He dipped his hand in, feeling the chilled water glide along his hand. While cold, it wasn’t unpleasant, and this part of the river was perhaps shallow enough to wade in. He didn’t feel like risking it though - didn’t want to risk falling and perhaps drinking in some of the water on accident 

He wondered, however, what the river did. Most threats to Gravity Falls had bad feelings from the get go, but this one just… didn’t feel dangerous at all. Dipper’s usual anxiety wasn’t here. The weather, the cool water, the peace of it all. For the first time in what felt like weeks, he was pretty much completely at ease. 

And he decided to enjoy it. 

He grabbed the book with his dry hand, wiping off his wet hand on his shirt before taking off his shoes one-handed and sitting himself at the riverside, dipping his feet into the river, and doing another read through of the journal. His favorite hobby. 

Time passed, and when the preteen finally felt the cold water numb his toes, he decided that it was time to head back to the shack. He got himself out, and put the book back in his vest. He could feel himself growing hungry and if he didn’t get back in time, he’d be stuck with frozen burgers. Again. 

Once the boy stood up, a numbing sensation suddenly went through his legs, falling to his knees with a gasp. “What… “ he managed before feeling a cloudiness to his mind. His whole lower body felt like it had fallen asleep - pins and needles that crawled up his back and reverberated through his head. There was a buzzing noise that was causing the boy to begin to freak out as a headache hit him. He grabbed at his head, and the clouding sensation suddenly became overwhelming, and he abruptly fell to his side - passing out. 

\-----

When Dipper woke up, several hours must have passed, because the shadows were high and red, though it took him a moment to see clearly. He groaned, an eye twitching as he pushed himself up and rested momentarily on his forearms. 

He ran a hand through his hair, clearing his forehead of grass before his hand… caught something. It was small, like a… bump? He sat himself up quickly, running a hand over it again, knocking his hat off. He then reached the other hand, and felt another! Two? What the heck were they? Horns??

His panic escalated, and he pulled his hands over his ears… until he felt something fuzzy and removed his hands from the side of his face. He could feel himself hyperventilating as he grabbed at the fuzz and realized that they were his… ears?? He went to stand - ready to run home while freaking out. 

When he did stand - things just completely felt wrong. He felt like he’d moved muscles he didn’t have, and when he finally looked down, he squealed 

“AH! HOOVES? DEER? DEER HOOVES?” He looked back at the rest of the body - he had 4 legs! Four legs! “Centaur!? Deertaur?!” He panicked even more, grabbing the Journal out of his vest and scanning the pages on the river again. 

There was _nothing_ in the book about transformations, hell there wasn’t even anything about deertaurs! He desperately searched for anything about it - more importantly, turning back. And he couldn’t find anything “.... Great” he groaned, seeing that his hat had fallen off his head. 

He huffed, gently walking over to the hat. The gait was pretty natural, and he didn’t find it _too_ strange to have 4 legs.. But bending over to grab the hat was proving to be a problem. 

Just as he finally got his hat, a voice shouted his name not too far away

“DIPPER??” 

… Mabel. 

Dipper could feel his already high blood pressure spike at her tambor. What was she even doing there? But as he looked up at the sky, seeing the deep reds, it was probably because he was out so late…

But then, he heard Soos. 

“Dipper!! Mabel’s worried!” 

Of course she got Soos to help her. 

Oh god, how was he going to hide himself? 

“I can’t let them see me like this!!” 

The poor boy began to panic, backing away from their voices and towards the river. He looked around, trying, trying to find some way to get away from them, and spotted the large log that he’d passed while looking to the river. He trotted - yes, trotted - behind it, but it seemed that he couldn’t hide - the whole deertaur thing gave him a few inches in height. 

He’d have to sit - something he didn’t think he knew how to do. 

“Huh? Oh, Mabel! I see him!” Soos shouted, waving to Dipper . The poor boy hoped that his ahem, new stuff (?) was hidden well enough behind the log

“Hey, Dipper!” Soos gave the kid a smile, and Dipper tried to smile back - it unfortunately looked more like a grimace. 

“Hey Soos…” The boy started “What - uh - what’s up?” 

“Been lookin’ all over for ya, lil’ dude. Where ya been?” The older man asked. Dipper let out one of his painfully awkward laughs. 

“Oh, I just… took a nap! You know, cause its so nice out and stuff-” 

“Dude” Soos interrupted “Are you… taller?” He questioned, squinting a bit. 

“Ahaha! So you noticed my growth spurt?” Dipper attempted to play it off, though Soos could probably see through it

“... What’s goin’ on, little dude?” Soos asked “Did you find that size crystal thing again?” 

“Uhhhhh where’s Mabel? I could’ve sworn-” 

“WHOA” 

Dipper startled and turned around, seeing Mabel standing next to him. 

“M-M-Mabel!” He shouted back, nearly angry, but mostly scared. 

“... What the heck, Dip?” She asked, fascination clear in her tone. 

“Mabel, what are you…” Soos started, before looking over the log and seeing Dipper’s … furry bottom half “... Holy smokes” 

Embarrassed, Dipper began to back up “Don’t - don’t come any closer!” 

Mabel immediately gave him an unimpressed look. 

“Dipper, you’re a… DEER, not like, a WOLF” She explained, coming closer to him and grabbing at his arm. The movement caused his deer-like ears to pop up from under his hat “.. Oh, my, GOODNESS!! That’s so cute!” She squealed, all of her shock dissipating. 

“... What happened, man?” Soos spoke up, and Dipper looked over to the river, just as his sister tried to touch his ears

"MABEL!” the boy snapped, and she pulled her hand back with an awkward chuckle

“Sorry” she shrugged sheepishly and Dipper groaned

“I dipped my feet in the water of the river and… Poof!” he raised his hands for effect “The book doesn’t have any information on it” 

“Well, we gotta get back to the Shack, Dipper, its gonna rain soon!” Mabel pointed up to the now cloudy sky. 

“What?? I can’t go back like this!” Dipper exclaimed “What if - Grunkle Stan-” 

“Dipper, we’re not leaving you in the forest” Soos said with some authority. Dipper just made a face at the man “I’m not above carrying you, dude” 

His adorable little deer ears lowered in defeat. 

“Fine, fine” The boy grumbled. Soos moved off to the side to allow Dipper to start walking, and to everyone's surprise, his gait was relatively quick - at least at first. 

As they started back to the Shack, rain really started to come down, and Dipper - nervous as he was, nearly fell into the muddy ground before Soos caught him, and ended up carrying him anyway. Dipper seemed a bit miffed about it, but didn’t complain outright. 

Once they arrived, it had really begun to pour, and it was nearly pitch black. Dipper was relieved once they were under the rickety porch roof and into the house, opening the door with Mabel following right behind and barreling past them. 

“Grunkle STAAAAAN!” Mabel called out “We got DIpper! You Gotta see this!!” 

There was, initially, no response

“... Grunkle Stan?” 

THUNK

The trio turned their heads to the front door, where Stan had just entered and raised a brow at the three “Welcome back what haa-” His eyes fell on Dipper, who was still being held by Soos, embarrassingly enough. He straight up just stopped mid sentence, and stared at the boy, whose ears flattened to the side of his head, and his face turned red at the staring. 

“What… what the heck happened?!” The older man asked, hand on his forehead. 

“I uh….” Dipper tried to start “... I don’t really know” he admitted

“He’s so cute!” Mabel interrupted “ Look at his little ears!” 

Dipper slapped away her hand, which was reaching to pinch his cheek “Shut up!” 

“...” 

Stan just continued to stare, bewildered beyond any proper concept of belief. He inhaled, pinching the bridge of his nose just above his glasses, and sighed deeply. 

“Kid, you get yourself into the weirdest, most ridiculous - i mean, how the heck did this even!?” he exclaimed, unable to form a more proper sentence “You know what, i’m going to assume we’re all having some weird collective dream, and we’ll all be fine in the morning. And if not! I’ll deal with it then” He concluded. “Lets just get you rascals fed and in bed” 

Dipper just nodded along. He was honestly kinda hungry anyway. 

“Soos, can you put me down?” The boy asked. 

“Aw, but you’re so fluffy and cute!” 

“Soos!” 

“Hehe, sorry dude. Just teasing” the man reassured, putting him down on the tiled kitchen floor. The boy managed to stand for all of a few seconds before his hooves lost all purchase and his legs slid out from under him like Bambi on ice. 

“Carpet, carpet!!!” Dipper squealed, and Soos promptly picked him back up and marched him over to the living room carpet, placing him down and letting his stand stabilize. “Th-thanks Soos” 

“No prob, dude” The man reassured with a pat to his head. 

Once dinner was over and Soos had left for the night, Stan had been the one to bring “Deer-per” as Mabel had started calling him (he hated that nickname even more than “dip dop”) to bed. 

Dipper let out a sigh as he “lied” down in his bed “Stan, you sure we’ll figure out what happened?” 

“I mean, i’m still banking on this being a very wild dream brought on by drinking some very expired milk, but yeah, if it's still legit in the morning, we’ll figure it out, kid” His Grunkle pat his shoulder as reassuring as he could “So long as this isn’t some long con, kid” 

Dipper glared, and the man couldn’t help but laugh. 

“Just go to sleep, Dipper” Mabel called from her side of the room with a grin “Maybe it’s a spell that’ll fade in the morning!” 

“... Maybe” He resigned, looking at his deer half and noticing the little spots. He quickly covered it with a blanket before thinking about it too hard, and pulling out the book. He’d wanted to at least *try* to forget for a little while. An attempt will need to be made if he’s to sleep at all. 

By the time he did sleep, he’d forgotten why he’d gone to the river in the first place

He was woken that morning by a distressingly familiar girlish scream coming from the bathroom. The sheer volume caused him to shoot up - including onto his hooves- and fall right out of bed. 

“Huh, wh- Mabel?!” He quickly stood, and wasn’t really focused much on the fact that he had *galloped* over to the bathroom door and subsequently froze in place. 

Flopping - quite literally- in the bathtub was Mabel. From the waist up, at least. Right below her stomach was a pink, scaly tail, and a flamboyant looking flipper at the end of it. Despite the situation (or perhaps, because of it?) she didn’t even look scared. In fact, she looked…. *delighted*

“Dipper! Dipper look!!” She flicked the tail “i’m a MERMAID!!” She grinned, and he looked back up at her face - seeing that her ears were now fins, tinged the same hot pink as her tail, and were flicking about with her excitement. 

“G-G-GRUNKLE STAAAAAAN!” Dipper called out, but after a few seconds without a response, he looked back at Mabel “Stay… hydrated” he ordered before leaving the doorway, yelling down the stairs once more. 

Nervously looking down when he got no reply, he took in a deep breath and, slowly, agonizingly, walked his way down the stairs - hands gripping the railing like his life depended on it. Hoof by hoof it probably took almost 10 minutes. 

Once he’d found his footing on the rough wooden floor, he started yelling again in earnest “Grunkle Stan, this is an emergency!!” he headed towards the kitchen, stopping right in the doorway and letting out a startled “NYEH!!” noise that - was he not frozen in shock - he would have been very embarrassed to have made. 

There was a stone… _thing_ lying on the tiled floor of the kitchen. Whatever it was was large, had wings, and it started to get up just as the familiar feeling of “fight or flight” hyped itself up from his regular 7/10 to a sky high 15. He could feel the need to flee in his bones as the massive thing finally seemed to have a shape. 

He turned, and looked down at him. 

“... Dipper?” Stan voiced, looking at the petrified expression on his grand nephew’s face. Stan knew he looked different. One drink from the tap and… poof! He was all grey, and felt like he weighed a ton. He really wasn’t sure what had happened, honestly. 

“G-g-g- GRunKLE StaAAAAAANNNN” Dipper backed up, slipping slightly as he did so. 

“Dipper, kid, stop screaming, its me!” The man panicked right along with him, seemingly reaching out to help steady the fawn, but the boy let out a shrill yell at the action. Stan simply decided to lift him up, getting purchase on the deer portion of the body. 

“YouRE FReaKInG mE Out Put ME DowN!!!” The boy shouted, trying to push the cold hands off of him. 

“Upstairs first!” Stan announced, trying to maneuver through the living room and up the stairs, Dipper ending up stuck under one of the man’s arms, scrambling and yelling about how freaked out he was. Once they got up the stairs, Stan put the fawn down, letting him stand on his own power and take deep breaths. 

“You done freaking out on me, kid?” 

“I…. I think so….” Dipper managed, his little deer ears suddenly perking up “Wait-wait Grunkle Stan, Stan, its Mabel! She’s-” 

“A MERMAID!!” The girl called from the bathroom with a rather gleeful tone! Stan turned, and stared in utter bewilderment at her shining, pink tail. “Whoaaaaa” Mabel stared right back “What are _you_?” 

Stan continued to stare, then looked back at Dipper, who had grabbed that damned book and was holding onto it for dear life. Stan's brain racked for what to do, and contemplated if he should continue playing dumb… but he had to make sure they were safe, first and foremost. 

“I uh… I have no idea what the heck happened!” he half lied “I mean, Mabels a mermaid, you’re a … deer thing.” 

“A deertaur!” Mabel chimed in

“And I’m… “ The older man looked down at his grey, hard skin

“A Gargoyle!!” Mabel announced, still smiling like she’d just gotten a wish granted. 

“A what?” 

“Well, you’re made of stone, you got wings and horns, and your eyes glow! Like those gargoyles in that TV show that Dipper was obsessed with last year” She concluded, leaning on the tub-side. 

“Well, I guess that adds up” Dipper flipped through the journal, eyes scanning for knowledge on Gargoyles. “But like, that's just Cartoons. How are they… real?” 

“Does that even matter?!” Stan exclaimed “I’m still…. This!!” 

“A gargoyle!” Mabel corrected eagerly, grinning ear to ear with her braces glistening. 

“Yeah, yeah Mabel, i get that” he waved his hand “Just… stay in the tub” 

“Heh, I’m pretty good on that front, Grunkle” She slid herself down until only her pink tail showed. 

“Dipper just - just sit somewhere… I”m gonna call Soos, tell him not to come in today. Wendy too” Stan pointed to the bed and Dipper nodded - not even worried about not seeing his friends today. 

Stan watched as Dipped managed to get himself on the bed and sitting, and took out the journal, and on the after that, did Stan head back down the stairs. 

Picking up the phone with all the care the stone man could muster, he ended up having to use a pencil to dial - before hearing the doorknob shake and jingle. 

“Oh great” Stan groaned, looking at the door, earring a kind of gross sloshing noise, like when someone steps in mud. 

“Mister Pines?” He heard Soos “Uh, could you maybe open the door pretty please?” 

“... What’s wrong, Soos?” Stan called out, making his way to the door slowly 

“Uh I'm… made of mud?” The man answered, and a morbidly curious Stan opened the door. 

Standing (though that term was being used very loosely here) was a man made of dark, damp mud in the vague shape of his ever-reliable handyman - even wearing his hat. But everything else… 

Well, he looked like he was about to melt into a puddle at any minute. 

“Soos?” Stan questioned as the two stared at each other 

“... Boy, you got the better end of the deal, huh” Soos responded, staring at the gargoyle. 

“What… Yikes, what happened?” Stan put a hand through his hair - which was still hair oddly enough. 

“Dunno! Woke up this morning and I was just, all over the floor. Its super, super weird” Soos meagerly explained. 

“You’re telling me” Stan groaned “Just uh… stay out here. You’ll get … yourself all over the place” he stated, and Soos nodded - or at least Stan thinks he did. 

Stan went back upstairs and the kids hadn’t really moved much - Dippers head in that stupid book. 

“So uh, Soos is here” 

“Oh, good!!” Dipper looked up “Maybe he can help!!” 

“Oh yeah, he can’t help kid” Stan pinched the bridge of his stone nose “He’s some kinda… mud monster thing?” he tried to describe. 

“Wha- seriously?? I gotta see!! Someone empty the fish tank and take me downstairs!!” 

“Mabel, please calm down. We’ll get you downstairs… somehow.” Stan sighed. “Listen, just, give me a few minutes to think of something-” 

“Wait! I have an idea!” Dipper announced, managing to clamber off the bed and stand on his wobbly deer legs “Grunkle Stan, take me downstairs” The boy requested and the man nodded, reaching over and picking up with grand-nephew with ease. 

After getting the boy downstairs, he instructed Stan to empty the saltwater tank into the sink (with the plug in, the fish were just gonna have to live with it), refill it with freshwater, and told him to get the flat-bottom wheelbarrow. 

“You’re a genius, kid” the man commented before heading outside. 

“Soos, I’ll be with you in a sec” Stan pointed at the semi-formed employee before headed toward the wheelbarrow, which was turned on its side. Soos looked a little more put together- if that meant anything. 

“Ah, no problem, Mister Pines” Soos replied “Are the kiddos okay?” 

“Mostly. Mabel’s got a fishtail for some reason” Stan answered “We’re working on getting her downstairs” 

“Oh, wow! I bet her tail’s pretty!” Soos commented just before Stan pushed the wheelbarrow into the living room. 

“Great! Now, put the tank in there and bam, she can go places!” Dipper announced, his fuzzy little deer ears perked up in pride. 

“Good thinkin’ kiddo. Lemme go get our fishy little nuisance” Stan turned and went back up the stairs, the boards creaking dangerously as he did so. 

Dipper sighed a bit and looked over to Soos, whose appearance made the poor boy jump 

“Soos?!” The boy’s ears perked up 

“Heya, Dipper! Lookin’ … uh… nice? I guess?” Soos's muffled voice greeted, waving a hand that was vaguely human looking - like wax slowly melting. Dipper shuttered, and took the book out of his vest. 

“Lemme see if what you are is in the book” He assured Soos, flipping through the book and glancing at every page until he found something that fit “hah!” He went up to show Soos the page on the porch. “You’re a clay -mud type monster! He calls it a Golem, but we’re not gonna call you that cause that's not the right word to use” Dipper attempted to explain. Soos just shot him a thumbs up as the boy pointed to it. 

“Makes sense to me” Soos replied, and looked past him at the stairs, where Stan had re-entered the room and was putting Mabel in the wheelbarrow. 

“Thanks for the idea Dipper!” Mabel grinned as she got settled “Now I can go places! Like the pool, or-” 

“Let’s slow down now, puddin-pop” Stan put a hand up “We’ve still got no idea what even happened!” 

“.... Wait, I do!” Dipper voiced, flipping the pages back to the spread on Fluvius Cantatis. He showed the page “This is the river that gravity falls is getting its water from!” 

“What? Why did we change rivers?” Stan asked with a quirked brow. 

“I heard it’s cause the other rivers got lots of junk in it and they’re trying ti clean it” Mabel shrugged “I think it's supposed to be only temporary” 

“Yeah” Dipper nodded, having heard that as well. He started scanning the page again “There's nothing in here about like, a cure, but the author seems flippant about it so… maybe this is all temporary?” 

“Wait…. Uh, if all of Gravity Falls is getting their water from that river…” Soos commented. 

“... That means….” Mabel’s face showed a concerned fascination, but then looked at Soos and her brows raised “Wha- Soos?? Wow!” 

“That means… everyone is going to be a monster” Dipper ended up finishing for her, while Mabel stared excited “... oh… we gotta call Wendy! Hoooly-”

“Hey, hey, hey, worry about yourself first, kiddo.” Stan prioritized. “Listen, i’m sure that other than frazzled, people will be fiiine” Stan lightly patted the boy’s shoulder “Now uh, breakfast? We can eat outside or something? I feel bad lot lettin’ Soos in but he’s uh… dirty” 

“I wanna see Soos!” Mabel announced “I want him to see my tail!” 

Stan obliged her, wheeling her transportable aquarium out to the porch and leaving Dipper alone with the book. 

Dipper really, really wasn’t sure what to do next.


End file.
